Reducing vertex density as distance from point increases
If all you need is to reduce vertex count, and not care much about the topology, you may consider use Decimate modifier, and control the modifiable area by vertex group.

Method 1:



Method 2:


Select the ears, then CTRLI to select the invert part;
X > Limited Dissolve to dissolve elements for mesh simplification in a relatively cleaner way.
Press F6 for further tweaks.




P.S.: Limited Dissolve gives same result as the Decimate Modifier by using its Planar mode. So you can use both.

(Head model came from Sintel project)